This application is related to and claims priority from Japanese Patent Applications No. 2000-261094 filed on Aug. 30, 2000, and No. 2000-365510 filed on Nov. 30, 2000, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a double heat exchanger having several heat-exchanging portions such as a condenser and a radiator, in which different fluids having different temperatures flow, respectively.
2. Description of Related Art
In a conventional double heat exchanger described in JP-A-8-178556, a first heat exchanger and a second heat exchanger are connected by side plates to be integrated with each other. Further, for reducing heat stress generated in tubes of both the heat exchangers, a recess extending from one longitudinal end toward the other longitudinal end of the side plate is provided. However, in this double heat exchanger, the recess extending in the longitudinal direction of the side plate is need to be elongated enough for sufficiently reducing the heat stress generated in the tubes. Accordingly, strength of the side plates is reduced, and a performance for holding and fixing both the heat exchangers is deteriorated.
In view of the foregoing problems, it is an object of the present invention to provide a double heat exchanger which can reduces heat stress generated in tubes while preventing strength of a side plate from being reduced.
According to an aspect of the present invention, in a double heat exchanger having a first core and a second core, a side plate is disposed at one side of the first and second cores to extend in a direction parallel with first and second tubes of the first and second cores for reinforcing the first and second cores, and the side plate is disposed to be connected to both first header tanks and both second header tanks at connection portions. The side plate has a flexible portion disposed to be flexible at least at one side of the connection portions, and a recess extending from one longitudinal end of the side plate until the flexible portion in a longitudinal direction of the side plate to separate the side plate at the one side of the connection portions. Accordingly, even when heat expansion amount is different in the first tubes of the first core and the second tubes of the second core, heat stress generated in the tubes can be absorbed by the deformation of the flexible portion. Further, because the recess extends from the one longitudinal end of the side plate until the flexible portion in the longitudinal direction of the side plate, the recess can be made shorter. Thus, in the double heat exchanger, the heat stress generated in the tubes can be reduced while it can prevent the strength of the side plate from being reducing.
According to an another aspect of the present invention, in a double heat exchanger with a first core and a second core, a side plate is disposed at one side of the first and second cores to extend in a direction parallel with first and second tubes of the first and second cores to be connected to both first header tanks and both second header tanks at connection portions, the side plate has a recess portion extending from one end in a direction crossing with the longitudinal direction of the side plate at least at one side of the connection portions, and the recess portion has a recess top part curved by a curvature radius larger than a predetermined dimension. Accordingly, even when a heat expansion amount in the second tubes is different from that in the first tubes, heat stress generated in the tubes can be absorbed by changing an opening area of the recess portion. Further, because the recess top part is curved by the curvature radius larger than the predetermined dimension, it can prevent the stress from being collected at the top end of recess portion. Therefore, it can prevent a crack from being caused at the top end of the recess portion. Thus, a durability of the side plate can be improved while the heat stress generated in the first and second tubes can be absorbed. Preferably, the curvature radius is equal to or larger than a thickness of the side plate. In this case, the durability of the side plate can be further improved.